Core and mold wash



' applied tothesurface of latented Feb. 5, 1935 PATENT OFFICE 001m ANDBIOL'I) was]! Julius J. Calif asslgnorto 00-, San mm,-onm., acorporation-of Oflifomla This invention relates to 'orcoatings for'awlication' to foundry cores-"afidmolds-in j the casting of metals,wmchfr'quire a'high' particularly of "metals degree will be effective toprevent burning-in, erosion, or penetration of the metal into the sandor the f core or mold, or fusion to metal molds, gasificasurface, etc.,all of which defective castings requiring tion, pitting of the result inrough and costlycleaning operations to'make them serviceable.

Other advantages mold wash willappear tion;

As the fundamental requirements in a core wash for foundry use is asubstance which can'be the core or mold which will resist the great heatof molten-metal, many attempts to produce satisfactory mixtures offinely ground refractory materials with water or other-liquid, togetherwith a suitable binder, have been made. The various refractory agentsused heretofore include silica, graphite, magnesia, lime, aluminumoxide, fire clay, etc., and the binders such as oils, molasses, sodiumsilicate, starch, glutrin, pitch, resins, etc., but while most of thesemixtures appear to be suitable for some particular use, they utterlyfail in other situations, so that it may be said that no universal corewash has heretofore been developed nor has any practicable wash beendeveloped which would stand up properly under the intense heat of steelcasting without causing defects in the castings.

The core wash which I have developed will stand all heats up to severalthousand degrees, will permit of application of several coats and forceddrying without cracking, develops no pinholes or rough spots on thecastings, and always insures a smooth surfaced casting requiring thevery minimum of cleaning operations to finish them, is an inexpensivemixture easily applied either by brush or spray, adheres either to sandor metal molds and cores, yet does not choke the necessary pores of finesand cores and molds.

The important ingredient in my compound is finely divided mica, thoughits combination with the other ingredients seems necessary to get thefull benefits of the invention. The other ingredients (in the formula asdeveloped for highest heat resistance such as in steel founding) aretalc, silica, and china clay (kaolin). The materials are all very finelyground, preferably to pass of my improved core and in the followingdescrip- Application-W11, Serial No. 658,382

, 4 cum. (on. zz- -rasy or heat temeit gihem, and the principal objectofthe invention is to provide a wash of the kind mentioned which time Ia 250 proportions-are as follows:

1 mixing machine. Chinaclay 2 I It is furnished in dry form to thefoundryman' who simply mixes some of the powder with water to theconsistency or cream "and applies it to the cores or molds by brushing,spraying or dipping. Theabove is thepreferred mixturefor use in. castingsteel' where the temperatures to about 3000 F. as the coating producedbythe wash has been found to resist directly applied heats as high as 6000F. for considerable'periods oftimewithout developing faults.

For usewith metals pouring at'lower temperatures, such ascast iron,brass, bronze, aluminum, aluminum alloys, and the non-ferrous metalsgenerally, a modification of the compound has been found more suitable,and is as follows:

Parts g Mica 1 I J Silica 2 Intimately mixed as before. Graphite -1 Thegraphite to be crystalline or amorphous and of a high graphitic carboncontent.

It will be noted that clay has been omitted in this mixture, as it wouldtend to choke the pores of the very fine sands used in some non-ferrouscasting. In use the powder is mixed with molasses water (about 1 part to100 parts) and applied as mentioned. In place of molasses water anyother binder commonly used in the foundry may be used.

The first formula given is self-bonding and after drying by the usualmethods as by baking or torch will permit free handling of the cores andmolds without danger of injury to the coated surfaces. The absence ofany organic or oil binders is very important in steel castings as theseare generally the cause of pinholes, blows and other surface defects.

The second formula incorporating graphite will reduce the formation ofoxides on the surface of the castings, but is subject to objectionableabsorption in steel castings, sometimes giving rise to hard areas,whereas with the cores and mold coated with the first mixture thecastings are as smooth as good iron castings and homogeneous in quality.

If the wash is of proper consistency usually one coat will be foundsufllcient, but another coat or iimnmatiy mixedin a mesh, orefiner, andthe preferred two may be applied without danger of peeling, scaling,flaking, or cracking. In all cases sand cores protected with my improvedwash will be found to collapse after casting and the sand to leave thecasting easily without the aid of tools, with a result in smoothinterior surfaces on the castings free from defects. The same result issecured on the exterior surfaces when the wash is applied to the molds.

The micais chiefly responsible for the extraordinary results obtainedwith the compound and I believe it is due to the fact that thissubstance even though finely ground is of a scaly nature with theparticles more or less in overlapping arrangement, but strange as it mayseem the complete mixture appears considerably more resistant to extremeheats than any of the constituents alone.

There are several varieties of mica such as muscovite, paragonite,lepidlite, zinnwaldite, biotite, and phlogopite, all of which whensuflicient- 1y pure have been found to yield good results.

The tale raises the heat resistance and also aids in proper mixing ofthe powders, and the silica seems also to combine its influence withthat of the mica in raising the heat resistance of the mass, whereas theclay combines the properties of heat resistance with that of a binderable to withstand high temperatures.

It will be evident from a consideration of the invention, that once theformula is disclosed it is possible for anyone to vary its proportions,or incorporate other ingredients, and any such variations coming withinthe spirit of the invention are intended to be covered in my appendedclaims, and while I use the words coating for foundry cores" in myclaims, this is descriptive merely and is intended to cover the mixturewhether in the form of a liquid. paste or dry powder, also whether to beused on cores or molds of either sand or metal.

I therefore claim:-

1. A coating for foundry cores containing finely divided mica, talc,silica and clay.

2. A coating for foundry cores comprising substantially three parts 01'mica, one part of talc, one part of silica, and two parts of china.clay, all in finely divided condition intimately mixed together.

3. A coating for foundry cores comprising substantially three parts ofmica, one part of talc, one part of silica, and two parts of china clay,all in finely divided condition intimately mixed together and withenough water to make a paintlike mixture.

4. A coating for foundry cores containing mica and clay, the mica beingin prepondering amount and both ground to very fine condition adapted tomix with water to form a cream-like mixture for applying to the cores.

JULIUS J. HORAK.

